Great Neapolitan Earthquake of 1857/Part II. Ch. V

by Robert Mallet

CHAPTER V.

ENTRANCE TO THE MOUNTAINS AND TO THE REGION OF RUIN—EBOLI—CASTELLUCCIO.

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The buildings of the Locanda di Vozzi, at Eboli, are those of an old, suppressed monastery of the Riformati, of great size, nearly square, and not far from cardinal, but two stories above ground, and extremely well circumstanced for observation.

The front with the campanile (Photog. No. 124, bis) along the main road bears 23° W. of N. Its internal construction, generally, consists (block plan, Fig. 127) of a central interior court, surrounded by a double range of rooms with a corridor between, running right round the whole building. Two of the corridors, and a few of the largest apartments, are vaulted with brick or rubble arching; the others, as well as nearly all the rooms, are timber floored. The rooms are chiefly small, having been formerly monks' cells, and separated chiefly by walls of one brick thick. The external walls generally are 22 inches thick, of stone. There are four huge external buttresses on the south side, up to the level of the first floor, built after the shock of 1851, which shook the building a good deal. There is a stubbed old cylindrical tower at the N. E. quoin, and a small external terrace and building at the S. E. one. The

Photo Pl. 123		Photo Pl. 124
	⁠
Vincent Brooks, lith. London.
West Flank. Eboli.	⁠	East Flank. Eboli..

N. snd S. corridors are vaulted, the E. and W. ones timber floored.

The whole building is fissured in almost every part and yet not uninhabitable, all the fissures being narrow, and but moderately inclined, and its peculiar cancellated structure has, by the help of the mid lines of corridors, kept the roofing uninjured nearly.

The fissures that are most instructive, are those in the external quoins, those on the soffits of the arching, and at the junction of the cross walls between the rooms (or cells) and the external walls.

The fissures resulting from the shock of December last are readily distinguishable from those of 1851. The walls have been all limewashed more than once, in the interval of time between, so that the former fissures are filled and obscured, those of December last, new, clean, and empty. The largest fissures are open 0.3 to 0.5 inch in 10 feet. They are wider, larger, and more numerous on the S. and E. wings. The width of similarly circumstanced fissures on the E. and S. wings are on the average of eleven pairs as 7 : 6.5. The angle $(\theta )$ made by the path of the wave with the east flank wall, therefore, was

$\mathrm {Tan} \,{\theta }={\frac {6.5}{7}}=.93$ nearly,

or $\theta =43^{\circ }$, but the building is ordinal 23° W. of N., adding this, we have the azimuth of the wave-path at Eboli = $43^{\circ }+23^{\circ }=66^{\circ }$ W. of N.

None of the photographs (Figs. 124, 125, 126, Coll. Roy. Soc.), were taken sufficiently near, unfortunately, to show with distinctness any external fissures in this building, nor to show the S. W. angle at all. Referring to the block plan and elevation (Fig. 127), however, some large fissures in the external walls of the projecting buildings over the terrace, and, generally, in that portion of the structure, give an angle of slope with the vertical = $15^{\circ }$ to $16^{\circ }$, and allowing for the change due to the ordinal of the building, indicate an angle of emergence for the wave-path $e=18^{\circ }$ from the E.

The church was the only other building I could find at Eboli giving distinct indications. It is almost cardinal, and shows some pretty extensive sloping fissures in the walls of the apse, behind the altar, and in the N. wall of the nave, these being respectively nearly orthogonal. The apse fissures are comparatively insignificant, and from the form of the walls difficult to compare with those of the nave. The general deduction as to wave-path, however, coincides pretty nearly with that from the Locanda, being E. to W. and some degrees to the N. of W. The slope of the fissures in the N. wall of the nave gives for the angle of emergence $e=21^{\circ }30'$ from E.

The people generally at Eboli, and more particularly those of the family of the Padrone at the Locanda, state, that they experienced both shocks from E. to W., and that there was a considerable amount of vertical movement (sussultatorio).

A very intelligent man living at La Sala, but who was at Eboli on the night of the shock, whom I met at the Locanda (but whose name, I regret to find, I did not note), agreed with their notions, but thought he had also felt a sharp jerking shock from the N. or E. of N. directly after both the first and second principal shocks. If this be so, it would probably be accounted for, as a reflected wave from the high hills that overhang Eboli to the N. and N. E. No one heard any noise attending the earthquake.

The level of the ground on which the Locanda stands, as given by reduced barometer observation, is 326.8 feet above the sea. Barom. reads 29° 72', thermo. 50° Fah. at 9^h 25^m, Nap. m. t. (26th February).

At the Locanda of Eboli, I had the good luck to fall in with Signor Palmieri, the engineer of the corps of Ponti e Strade, to whom I had a letter from the Intendente Ajossa, and during the evening spent with him I obtained a great deal of useful local and other information, as to matters of fact from him.

He gave me circumstances I deemed conclusive, that the wave-path had been from N. to S. at Lago Negro and at Sapri, and at Laurino from the S. W. to N. E. I fell in again with Signor Palmieri near Polla, whence he was returning, and was indebted to him for first calling my attention to the instructive facts developed at the Palazzo Palmieri there, which he had just been examining.

About four miles from Eboli I crossed the Salaris by a grand old irregular bridge of one very large semicircular arch and several minor ones, and here first observed masses of the limestone pebble breccia, of the Apennine formation (the bridge is built of it), which, from this eastward, appears to overlie the limestone and underlie the deep diluvial clays and gravels of the valley bottom. The pebbles hereabouts are usually from two to four inches diameter, much water-worn and rounded, of a brown-grey and fawn-coloured argillo-calcareous rock, with a good many occasional pebbles of a tea-green, cherty, metamorphic slate, so hard as almost to resemble Jade. The cementing material is calcareous, and the interstices of the pebbles are filled with fine gravel and calcareous sand. It is a coarse but good building stone, and indurates much on exposure. In situ, this breccia here is stratified in great coarsely-defined and irregular beds, which generally approach the level in strike, though much tilted transversely to the line of valley.

At the fork of a small stream, the Merdarolo (or Pagliardo according to some of the peasants), where it joins the Salaris on the left bank, beds of limestone tilted almost vertically appear with a lithological character almost identical with our English lias limestone. They are unconformable with the enormous pile of limestone beds, nearly horizontal in strike along the valley, but dipping sharply to the south, which form the huge, shattered, and decussate precipices, rising to the summits of La Scorza or Monte Alburno. These summits shut in the Piano of Savanuola, a singular irregularly oval-shaped, and mountainous table-land, of more than twenty square miles in surface, and, beyond it, I get occasional glimpses of still higher ridges and peaks. The range of Alburno must rise to at least 3,000 feet above the plain between Eboli and the sea, and is now (12th February) covered with snow, for about half the depth down from the top, wherever it can lodge upon its abrupt and precipitous flank.

For about the lowermost third in height on both sides, the valley is covered with smoothed, rounded, and sloping masses of diluvial clays and gravels, with huge angular blocks and boulders dislodged from above scattered here and there.

Noble natural oak forest, clothes much of this down nearly to the valley bottom, as in the days when Virgil wrote his third Georgic:—

"Asper acerha sonaris; quo tota exterrita sylvis
Diffugiunt armenta, furit mugitibus æther
Concussus sylvæque et sicca ripa Tanagri."

Through these and below them, the rain has cut into these clays in a surprising manner, and in many places they seem as if subsiding bodily, from off the steep sides of the hills, and melting into the muddy flood of the Salaris, which, a few miles further eastward, unites its current with that of the Rio Negro or Tanagro, falling in upon its left bank, between the towns of Contursi on the north and Postiglione on the south, right under which are the ancient and the new post-houses of La Duchessa.

Here the first walls actually prostrated by the earthquake become visible (going eastward). The old posthouse is now a roofless ruin, of walls standing two stories (without floors) or about 30 feet in height, about 250 feet long by 45 feet wide, built of rubble limestone, with ashlar quoins. None of the stones of the walls exceed about 6 ins. x 12 x 12, or 18 at most; poor masonry, but not ill suited to seismometry.

The place was damaged by the earthquake of 1783, and rendered uninhabitable by that of 1851. Its general length bears 135° E. of N. The fractures and fissures produced in December are clear and distinct from the old ones. In the sketch (Fig. 128), the portions coloured black indicate the

walls partly or wholly fallen; and the places of the principal measurable fissures are marked $ff$, &c. The fissures of the S. E. end when reduced, give 76° W. of N. for the wave-path, those at the opposite end 73° W. of N. the mean = 74° 30' W. of N. Those at the former end are pretty evenly and uniformly sloped, and at an angle with the vertical = 24°, giving that for the angle of emergence of the wave-path. Some of the fissures, however, gave an angle of emergence as steep as 32° or 33°.

This indication puzzled me much. The N. and S. direction of wave-path at Naples, and on the south side of the bay, led me to expect that I should find the focus of the shock had been somewhere at sea, under the Gulf of Salerno, or that of Polycastro; and this was supported by continuing to find that the wave-path from Salerno and southwards was W. and E. more or less. I was not shaken from this hypothesis, by finding that no traces of the incoming of a roller or great sea wave had been observed anywhere along the coast from Salerno downwards; but the finding these fissures at Duchessa, leaning off towards the south and east, seemed irreconcileable with any possible position of focus that could account for the observed wave-path at Naples, inasmuch as it could alone be the result of a focus to the eastward of Duchessa, and therefore far away from intersecting any line drawn nearly north and south through Naples. I summoned my faith in induction to my aid, however, and trusted to the witness of further facts to solve the mystery.

The postmaster here, had heard a sound along with the shock: he thought it came rather before the actual oscillation, which was undulatory also. He was standing up, in the room in which he slept, and described the sound at or preceding the first shock, "Not loud but a quick sort of deep hoarse buzz"—"Roco ronzio profondo vivace, ma piccolo." He could not tell whether there was any sound with the second shock or not—"he thought there probably was—but they were all in great alarm." One or two considerable fissures had been produced in the new posthouse. I took observation of the sun here to determine the magnetic declination, and give the result as worked out, but am satisfied I must have committed some gross error in the observation or note of it.

Duchessa, Lat. 40° 34' N., Long. 15° 11' E. (Feb. 13)

Hour angle at time of observation	= 24°	6'	48″.15
Sun's azimuth computed . . . . . . .	= 27°	42'	west.
Sun's bearing by compass . . . . .	= 20°	0'	east. (?)
Magnetic declination . . . . . .	= 47°	42'	east.

There is no ground for assuming any serious local disturbance of declination here.

From a little beyond Duchessa, off to the eastward, and rather to the south, Sisignano is seen perched upon a spur of Monte Alburno, that runs in a S.E. and N.W. direction diagonally across the main valley and down to the Tanagro. The road continues to rise rapidly, ascending over the shoulder of this, at the little village of Lupino, and to the south or right hand. The vast pile of limestone beds of the Alburno is seen stretching away with nearly horizontal strike, parallel to the general line of the great valley, and dipping sharply to the west and south-west, at probably 45°. The transverse ridge is too much covered to enable me to prove, what I conjecture from its outlines, that it consists mainly of the breccia limestone, unconformably laid on the beds of Alburno.

After about six miles, the highest point of the transverse ridge is reached, near Lupino, and I determined its height by barometer, which reads, at 1.32 Nap. mean time, 28.78 inches. Thermo. 52° Fahr. (13th Feb.). This reduced, gives 1441.3 for the altitude. (See Appendix for particulars of all barom. measurements and reductions, &c.) The transverse ridge here, is a complete dividing barrier, upon the south side of the Tanagro, between the great valley of the united streams of the Salaris and Tanagro, and that of the latter river, into which I begin now to descend again rapidly, to within perhaps 400 feet above the bed of the river.

At Lupino, almost no damage was done. The few houses are low, well built, and not very old. The postmaster here was rather uncommunicative. "They had been severely shaken and much alarmed, but knew of no damage done at Lupino. I should find plenty six or seven miles further eastward." I can see with the telescope the old château on the highest part of Sisignano, overthrown and in ruins, and a good deal of damage in the place itself. Gualdo, with Terra Nuova, are above me on the south, but neither have suffered very much. About two miles further on I pass the Taberna of Urma, a small post-house, with a new and yet unroofed Capella close to it, which had just been built, and the mortar of its limestone rubble yet fresh and soft. It was a building of one story, about 30 feet E. and W. by 24 feet N. and S., and the walls about 17 feet high. These are fissured, at three out of the four quoins in such a manner, that the ends tend to come out. The fissures are widest at the east end. The axial line is exactly cardinal by my prismatic compass, and the fissures give a wave-path of 81° 30' west of north. The stones are large in proportion to the size of the building, and I can get no indication reliably as to emergence.

Numbers of fissured buildings now begin to present themselves, all indicating as I pass them a general east and west direction of wave-path. A little further on, after passing a torrent that falls into the Tanagro from the south, I look up in extremely steep lateral valley—Il Vallone Petroso—in which many loose surface blocks of limestone, show themselves to have been shaken from their positions and rolled over: from the road at this point there cannot be less than 3,500 feet vertical, of calcareous beds above me. The geological evidences of violent dislocation and elevation at all sides in the mountain formation are strikingly grand.

At the 58th milestone from Naples on the military road I am close under Castelluccio, a strange, immured, and gloomy-looking mediæval town, perched on the very crest of a solid, rounded, lumpy mass of limestone, showing little or no signs of distinct bedding, and with its sides so steep, that trains of loose stones lie in huge furrows, straight up and down its flanks here and there. The Tanagro flows at the opposite side or round to the north of this hill, while its tributary from the Vallone Petroso winds round the foot of the enormous rock, (see Photog. No. 13, Part I,) to join the former to the N. E. The town and its eminence thus stand upon a sort of peninsula, rising more gradually from the main valley upon the westward, and having the longer axis of the rocky mass nearly in an E. and W. direction.

Although close enough to see the joints of the masonry in its walls, through the keen clear air, with the naked eye, I found it would require four hours' time to climb up to the town; and learning that it had sustained but very little damage, I did not attempt to lose time in the ascent, but scanned it narrowly with the telescope in a fine light. Not a single fissure was visible in the N. W. or E. sides of its external walls, which, although they look like those of a large fortified mediæval town, are in reality only the rear walls of the houses turned outwards, and built closely together, and upon the very edge of the steepest scapements of the rock. Such are the characteristics of many of these most interesting old towns.

But I can see that the top of the cupola of the highest campanile or tower in the place, probably that of the church, has been broken off short and is gone, obviously by the direction of the fracture, by a force from the eastward and a little south, or about 70° W. of N. by estimation (c, Fig. 129), being, as figured, at the east end of the cupola, which was an hexagonal, Saracenic sort of small dome, of limestone, obviously modern.

As I move round the base of the rock, I can see thus much reason for its comparative security, that the mass of solid limestone upon which it rests, presents its long way to the length of the valley, and lies nearly E. and W., with its steep end towards the east, and buttressed away to the westward by a longer slope, as in the section E (Fig. 130) taken in a line with $ab$.

Quite beneath Castelluccio, between the road and the torrent, that rushes to the Tanagro round its base, and some 100 feet below the road level, is a solitary church, La Chiesa d'Incoronata. It stands upon a low lying spur of deep diluvial clay and gravel, upon nearly the edge, that scarps sharply down, covered with natural oak and hazel, to the torrent of the Petrosa, and is greatly damaged; the whole of the east end having fallen out, carrying much of the roof with it. Upon descending below it, through the woods, I find that the deep diluvium above rests upon argillaceous beds, which are nearly vertical, and strike across the valley in a N. W. and S. E. direction, and so are almost parallel with the ridge of Sisignano and Lupino, already passed, and which appear to be wholly unconformable to the limestone breccia of Monte Carpineto; the subordinate mountain, to the continuation of the N. scarp of Monte Alburno, and which lies S. and S. E. of Castelluccio.

This church is a poor building, the walls about 15 feet high and 2${\tfrac {1}{2}}$ feet in thickness, of coarse limestone rubble, covered with a heavy tiled roof upon gross, ill-framed timber. The north wall had, in part, long leaned outwards (as I was informed by the priest), and a portion had fallen towards the north; but all the remainder of the east end had fallen outwards, or in a general direction of the line $a$ to $b$ (Fig. 131), and a much larger portion of the roof, as indicated by the irregular line $cc$, had come down and fallen within the walls. In both the north and south walls were some fissures $fff$, which, together with the general direction in which the mass of dislodged material had been thrown, indicated a wave-path of from 80° 30' W. of N. to nearly due W. and E. The mode in which the roof had come down, seemed to indicate a considerable amount of emergence in the wave-path, from the eastward, but how much, neither it, nor the direction of the fissures, in the coarse rubble, and through the heads of the windows, would indicate.

Monte Carpineto is part of a subordinate range, that stretches in a N. E. and S. W. direction, as far as Salvitella, northwards, almost at right angles to the great north scarp of Monte Alburno; the Tanagro piercing through it nearly at right angles, about half way between Petina, on the south, and Salvitella; and the much larger stream which comes away from far north of Muro and Bella, in the lofty recesses of Monte Croce, and joins into the Tanagro at Castelluccio, and properly should be called Tanagro, taking the name of the Bianco. The descent is extremely rapid from about the 59th milestone, or half a mile beyond; and as the new valley begins to open, I catch the first glimpses of Auletta, and even at this distance perceive the terrible evidences of the overthrow it has sustained.

Monte Carpineto once passed, the general direction of the main valley changes, and I descend into a deep and nearly closed-in hollow, between smaller lateral valleys running nearly north and south, and opening in common upon the course of the Tanagro, in which Auletta and Pertosa, each perched upon a separate spur or colline, and each in the mouth of a separate but closely adjacent valley, are situated.

Upon the south-east, this hollow is completely barred and closed in, by the mountain of Taliata at the west, and the ridges of Monte Sarconi on the east, which abut upon each other, with nothing intervening but the tremendous cleft, through which one portion of the Tanagro forces its way from the north end of the Piano di Diano; while another portion of it, disappearing there, finds its way by a subterraneous channel, nearly parallel with that sub dio, and both meet again at Pertosa; the subterraneous waters discharging from the mouth of St. Michael's Cave, at a level of about 200 feet above the open bed of the river, opposite Pertosa, and turning the wheels of some old Catalan iron forges, before falling into it.

Although from this point the Tanagro pursues the same direction, as lower down, nearly from E. S. E. to W. N. W., the whole character of the valley itself has changed since passing Castelluccio, it is no longer a great E. and W. valley, but an irregular deep hollow, produced by the abutting and inosculation, of several secondary mountain ranges and valleys, running more or less N. and S., and gradually shutting up the hollow, until Auletta and Pertosa seem enclosed within it.